Error code 5 is not consistently enforced in shift operators for shifted bits bigger than 256

[jeshecdom]

In the following contract:

contract Test {

   receive() {}
   
   get fun getBool1(x: Int): Bool {
       return 10 < (2 << x);
   }
   
   get fun getBool2(x: Int): Bool {
       return 10 < (2 >> x);
   }
}

• For << operator:

Calling getBool1(257) gives: Error: Unable to execute get method. Got exit_code: 4 (overflow error, meaning that it accepted the value 257 as valid). But interpreter responds with: Cannot evaluate expression to a constant: the number of bits shifted ('257') must be within [0..256] range.

Calling getBool1(7237005577332262213973186563042994240829374041602535252466099000494570602496) (i.e., getBool1(2^252)) gives: Unable to execute get method. Got exit_code: 5 (range check error). The interpreter response: Cannot evaluate expression to a constant: the number of bits shifted ('7237005577332262213973186563042994240829374041602535252466099000494570602496') must be within [0..256] range.

The above shows that << does not enforce that the shifted bits must be smaller than 257, because getBool1(257) actually attempts to compute 2 << 257 producing an overflow. Error code 5 is enforced for very big numbers only.

• For >> operator:

Calling getBool2(257) gives: false. But interpreter responds with: Cannot evaluate expression to a constant: the number of bits shifted ('257') must be within [0..256] range.

Calling getBool2(7237005577332262213973186563042994240829374041602535252466099000494570602496) (i.e., getBool2(2^252)) gives: Unable to execute get method. Got exit_code: 5 (range check error). The interpreter response: Cannot evaluate expression to a constant: the number of bits shifted ('7237005577332262213973186563042994240829374041602535252466099000494570602496') must be within [0..256] range.

The above shows that >> does not enforce that the shifted bits must be smaller than 257, because getBool2(257) returns false. Error code 5 is enforced for very big numbers only.

---

These examples are different from those in issue #2997 because in the current case, FunC does not simplify the expressions in the Fift code:

$Test$_fun_getBool1 PROCREF:<{
    2 PUSHINT
    SWAP
    LSHIFT
    10 GTINT
  }>
  $Test$_fun_getBool2 PROCREF:<{
    2 PUSHINT
    SWAP
    RSHIFT
    10 GTINT
  }>